Exercise 3 solution

import random

def gamete(rng, n):
    return tuple(rng.choice((0, 1)) for _ in range(n))

n = 3
rng = random.Random(11)
trials = 100000
same = 0
for _ in range(trials):
    child1 = (gamete(rng, n), gamete(rng, n))
    child2 = (gamete(rng, n), gamete(rng, n))
    if child1 == child2:
        same += 1
print(same / trials, (1 / 2 ** n) ** 2)

Output:

0.01583 0.015625

Reading it: Each child is a pair (one gamete from each parent). Two gametes match with chance 1/8, so both pairs match with chance (1/8) squared, 1/64 = 0.015625. The simulated fraction is close to it but not exact, because it is a random sample.